This invention relates to a process for the continuous production of beverage filter bags, especially tea bags with a hanging strip made from a carrier sheet material and with at least one pocket which consists of a filter material and is closed on all sides, contains at least one portion of a beverage substance, and is connected to the hanging strip; whereby individual beverage-substance portions are deposited in a row on a continuous web of filter paper of which a sleeve is formed, a string of consecutive, contiguous pockets, each containing one portion of the substance, is produced by individually sealing them off with a transverse seam, said transverse seam including both the trailing seam of one pocket and the leading seam of the following pocket, with perforations between the two seams along which neighboring pockets can be separated in the course of the process; the individual pocket is separated from the string of pockets; the pocket separated from the string of pockets is connected to a hanging-strip supply string; and the hanging strip is separated from the hanging-strip supply string.
Methods and systems for the continuous production of beverage filter bags and the filter bags thus produced have been in existence in numerous design variations. According to one such prior-art method, individual portions of an infusion substance are deposited on a continuous web of filter paper, a sleeve is formed, and by a transverse sealing process the sleeve is subdivided into individual pockets, each closed on all sides and each containing a portion of the substance. The sleeve can be produced by means of overlapping folds of the sheet of filter paper which are then sealed with a longitudinal seam, or by overlaying an additional sheet of filter paper and bonding the sheets with two longitudinal seams. The pockets are then attached to a hanging strip which permits manipulating and suspending the filter bag.
It is the objective of this invention to provide a simple process for the continuous production of filter bags of the type first above mentioned, which process operates reliably and at high speed and permits cost-effective production of the filter bags.
According to the invention, this is accomplished in that, for separating a pocket from the string of pockets, the continuously moving string of pockets is seized in a predetermined position near the perforation of the pocket to be separated and the forward speed of the string is accelerated in such fashion that the pocket is separated from the string by virtue of the relative movement.
An advantageous way to separate a pocket from the string of pockets is to guide the string of pockets to a continuously rotating wheel provided with recesses for individual pockets, where the longitudinal sides of the pocket to be separated from the string are seized by grippers laterally positioned next to the wheel and the relative movement between the grippers and the wheel causes the separation of the pocket from the string.
According to the invention, the pockets of the string of pockets are thus pulled apart at the perforation and individually separated. This separation process permits high-speed machine operation whereby in advantageous fashion 800 to 1500 and preferably 1000 to 1200 filter bags can be produced per minute. The grippers are advantageously designed to swivel in the direction of rotation of the wheel preferably via a cam mechanism which accelerates them in the direction of rotation of the wheel, thus producing the relative movement. In the forward movement of the string of pockets, a leading pocket to be separated is seized before the next following pocket is seized, and the leading pocket is accelerated at the moment the next following pocket is seized. In a further enhancement of the process of this invention, the forward grippers, as viewed in the direction of rotation of the wheel, seize a pocket that is to be separated from the string of pockets before the rearward grippers seize the next following pocket of the string, and the forward grippers are accelerated in the direction of rotation of the wheel as the rearward grippers seize the next following pocket of the string of pockets. The seizing movement of the grippers is preferably controlled by a cam mechanism.
In advantageous fashion the pockets, mutually spaced, are connected to the hanging-strip supply string. The inter-pocket spacing is produced as the pockets are pulled apart by the relative movement between the grippers and the wheel during the process of separating an individual pocket from the string of pockets. The pockets, preferably spaced apart by a few millimeters, adjoin the hanging-strip supply string so that the individually separated pockets are attached to a section of the hanging-strip supply string that corresponds to an elongated inter-pocket separation gap and will ultimately constitute the hanging strip of the filter bag. In another design enhancement, the spacing-dependent section length is augmented by advancing the hanging-strip supply string to the wheel at a faster rate than the string of pockets.
In an advantageous implementation of this invention, the pockets are held in the recesses of the wheel during the separation process, preferably by vacuum suction. The process thus provides for the individual pockets of the string of pockets to be positioned and locked in place in the recesses of the wheel. This also results in a uniform portioning of the substance in the pockets. As another advantageous aspect of the invention, the pockets are pushed or preferably blown out of the recesses in the wheel either concurrently with or following their attachment to the hanging-strip supply string. This makes certain that the pockets do not stick in the recesses of the wheel which would otherwise impede or interfere with the production flow.
The transverse seam is advantageously produced by fusion, preferably employing ultrasound. The perforation between the two transverse seams is best produced concurrently with or following the generation of the transverse seam, preferably by ultrasound concurrently with the transverse seam. The process according to this invention thus ensures a consistently identical transverse-seam geometry which significantly simplifies operation. In another advantageous form of implementation of the invention, the perforation is produced after the sealing of the transverse seam, using at least one rotating blade with a multigapped edge. The separate perforating operation extends the life and improves the quality of the ultrasound-generated transverse seam.
In advantageous fashion, the hanging-strip supply string for the filter bags is guided to the wheel during the course of the process and the pocket separated from the pocket string is attached to it by fusion bonding, preferably via ultrasound, either concurrently with or following the separation.
In a particularly desirable enhancement of the process of this invention, each one pocket from two pocket strings is bonded to the hanging strip at one common edge, with one of the pockets from a first pocket string being attached, along a suitably formed edge, to one side of the hanging-strip supply string and one of the pockets of a second pocket string being attached, along a suitably formed edge, to the opposite side of the hanging-strip supply string. Preferably in a first step one of the pockets of a first pocket string is bonded along a suitably formed edge to one side of the hanging-strip supply string and subsequently one of the pockets of a second pocket strip is bonded along a suitably formed edge to the opposite side of the hanging-strip supply string.
In an advantageous implementation of this invention, the pockets that are attached to the hanging-strip supply string are transported in that the hanging-strip supply string is grasped at specific points and pulled in the forward direction. In advantageous fashion the hanging-strip supply string is grasped at the point at which it connects to the pockets, preferably at the connecting point of every other pocket and most preferably at the connecting point of every fourth pocket. Advantageously, conveyance is provided by means of a belt equipped with mutually spaced cams which grasp the hanging-strip supply string and transport it by virtue of the movement of the belt.
A particularly advantageous design of this invention employs for the conveyance a controlled dual-belt system whereby in alternating fashion the cams of one belt move the hanging-strip supply string while the cams of the second belt are set in the transport position for the subsequent forwarding operation. According to a particularly advantageous concept of the invention, the movement of the belt is index-controlled, with the indexing flags or markers preferably positioned on the hanging-strip supply string. The pockets are advantageously attached to the hanging-strip supply string in the area of the indexing markers whereby, after a pocket is attached, the point of attachment of the pocket to the hanging-strip supply string is used to control the movement of the belt, thus indirectly constituting a quasi index-controlled system. Using a controlled and especially index-controlled dual belt system permits absolute positional precision in the movement of the hanging-strip supply string with pockets attached. This compensates for and eliminates any offset in terms of the proper positioning of a pocket on the hanging-strip supply string which could otherwise be a problem typically associated with the tolerances and deviations inherent in dual belt systems with spaced cams. In the process of this invention, a first belt of the dual-belt system, index-controlled via servo motors, moves into its transport position and jogs the hanging-strip supply string with pockets a specific distance. During that time the transport cams of the second belt are disengaged, to be brought into their forwarding position at just the right time for the further advance of the pocket-carrying hanging-strip supply string. Meanwhile, the speed of the second belt is regulated via servo motors which detect index markers on the hanging-strip supply string for instance with the aid of an optical sensor, causing an appropriate speed adjustment of the second belt which in turn brings the cams of the second belt into their transport position, grasping and moving the hanging-strip supply string with the attached pockets. As soon as the pocket-carrying hanging-strip supply string is grasped by the cams of the second belt, the cams of the first belt are disengaged and moved into their next grasping position.
For separating the hanging-strip section for the individual filter bag from the hanging-strip supply string, the supply string is suitably perforated at the point of the pocket connection, grasped in a predefined position near the perforation and subjected to an acceleration in the forward direction of the hanging-strip supply string in such fashion that due to the relative movement the hanging strip of the respective filter bag is separated from the hanging-strip supply string. In advantageous fashion the hanging-strip supply string is guided to a continuously rotating wheel in the process of which the supply strip is seized by grippers on the wheel, whereby the relative movement between the grippers and the wheel causes the hanging strip of the filter bag thus produced to separate from the supply string. For separating the hanging strip from the supply string the grippers, having seized the hanging-strip supply string, are suitably swiveled in the direction of rotation of the wheel and are accelerated in that direction preferably by means of a cam mechanism. The seizing operation as well is advantageously cam-controlled.